RRC ID 35463
Author Cobessi D, Dumas R, Pautre V, Meinguet C, Ferrer JL, Alban C.
Title Biochemical and structural characterization of the Arabidopsis bifunctional enzyme dethiobiotin synthetase-diaminopelargonic acid aminotransferase: evidence for substrate channeling in biotin synthesis.
Journal Plant Cell
Abstract Diaminopelargonic acid aminotransferase (DAPA-AT) and dethiobiotin synthetase (DTBS) catalyze the antepenultimate and the penultimate steps, respectively, of biotin synthesis. Whereas DAPA-AT and DTBS are encoded by distinct genes in bacteria, in biotin-synthesizing eukaryotes (plants and most fungi), both activities are carried out by a single enzyme encoded by a bifunctional gene originating from the fusion of prokaryotic monofunctional ancestor genes. In few angiosperms, including Arabidopsis thaliana, this chimeric gene (named BIO3-BIO1) also produces a bicistronic transcript potentially encoding separate monofunctional proteins that can be produced following an alternative splicing mechanism. The functional significance of the occurrence of a bifunctional enzyme in biotin synthesis pathway in eukaryotes and the relative implication of each of the potential enzyme forms (bifunctional versus monofunctional) in the plant biotin pathway are unknown. In this study, we demonstrate that the BIO3-BIO1 fusion protein is the sole protein form produced by the BIO3-BIO1 locus in Arabidopsis. The enzyme catalyzes both DAPA-AT and DTBS reactions in vitro and is targeted to mitochondria in vivo. Our biochemical and kinetic characterizations of the pure recombinant enzyme show that in the course of the reaction, the DAPA intermediate is directly transferred from the DAPA-AT active site to the DTBS active site. Analysis of several structures of the enzyme crystallized in complex with and without its ligands reveals key structural elements involved for acquisition of bifunctionality and brings, together with mutagenesis experiments, additional evidences for substrate channeling.
Volume 24(4)
Pages 1608-25
Published 2012-4
DOI 10.1105/tpc.112.097675
PII tpc.112.097675
PMID 22547782
PMC PMC3398567
MeSH Amino Acid Sequence Amino Acids / chemistry Amino Acids / metabolism Arabidopsis / enzymology* Arabidopsis Proteins / chemistry* Arabidopsis Proteins / metabolism* Biocatalysis Biosynthetic Pathways Biotin / analogs & derivatives Biotin / biosynthesis* Biotin / chemistry Biotin / metabolism Carbon-Nitrogen Ligases / chemistry* Carbon-Nitrogen Ligases / metabolism* Catalytic Domain Holoenzymes / chemistry Holoenzymes / metabolism Kinetics Ligands Models, Molecular Molecular Sequence Data Mutation / genetics Protein Binding Protein Multimerization Protein Structure, Secondary Protein Structure, Tertiary Recombinant Proteins / biosynthesis Subcellular Fractions / enzymology Substrate Specificity Transaminases / chemistry* Transaminases / metabolism*
IF 8.631
Times Cited 7
Prokaryotes E. coli JW0761-KC